1. Field of the Invention
The present invention relates to an image pickup apparatus that introduces light from an imaging optical system to an image sensor through an optical element array to perform image capturing.
2. Description of the Related Art
Image pickup apparatuses performing various operations on data acquired by using an image sensor to produce and output digital images have been proposed. For example, Todor Georgiev, et al., “Full Resolution Light Field Rendering”, Adobe Technical Report January 2008 and Todor Georgiev, et al., “Superresolution with Plenoptic 2.0 Camera”, 2009 Optical Society of America disclose image pickup apparatuses each capable of simultaneously acquiring two-dimensional light intensity distribution on an object plane and parallax information (hereinafter collectively referred to as “light field”) by using a technique called “Light Field Photography”. Such image pickup apparatuses enable, by performing image processing using the acquired light field, a post-image capturing process such as changing of a focusing position of a captured image (that is, refocusing) and adjustment of a depth of field.
However, in such image pickup apparatuses, it is necessary allocate pixels of the image sensor not only to storing of the two-dimensional light intensity distribution, but also to storing of the parallax information. Therefore, these image pickup apparatuses have a lower spatial resolution than image pickup apparatuses storing only the two-dimensional light intensity distribution.
On the other hand, Todor Georgiev et al., “Superresolution with Plenoptic 2.0 Camera”, 2009 Optical Society of America discloses a configuration in which each of lens cells of a lens array forms optical images of one certain point on an image plane formed by an imaging optical system on multiple pixels and at mutually different positions of the pixels. The camera synthesizes two or more small images thus acquired to produce a high resolution reconstructed image. Such a method achieving high resolution is called “pixel-shifting super-resolution”.
However, Todor Georgiev et al., “Superresolution with Plenoptic 2.0 Camera”, 2009 Optical Society of America describes a method of acquiring an effect of the pixel-shifting super-resolution only on a specific focusing position. Therefore, when producing an image (refocused image) whose focusing position is changed, change of the effect of the pixel-shifting super-resolution depending on the focusing position may decrease the spatial resolution.